Configuring non-Omnibus Redis for GitLab HA

This is the documentation for configuring a Highly Available Redis setup when
you have installed Redis all by yourself and not using the bundled one that
comes with the Omnibus packages.

Note also that you may elect to override all references to
/home/git/gitlab/config/resque.yml in accordance with the advanced Redis
settings outlined in
Configuration Files Documentation.

We cannot stress enough the importance of reading the
Overview section of the Omnibus Redis HA as it provides
some invaluable information to the configuration of Redis. Please proceed to
read it before going forward with this guide.

We also highly recommend that you use the Omnibus GitLab packages, as we
optimize them specifically for GitLab, and we will take care of upgrading Redis
to the latest supported version.

Configuring your own Redis server

This is the section where we install and setup the new Redis instances.

Prerequisites

All Redis servers in this guide must be configured to use a TCP connection
instead of a socket. To configure Redis to use TCP connections you need to
define both bind and port in the Redis config file. You can bind to all
interfaces (0.0.0.0) or specify the IP of the desired interface
(e.g., one from an internal network).

Since Redis 3.2, you must define a password to receive external connections
(requirepass).

If you are using Redis with Sentinel, you will also need to define the same
password for the slave password definition (masterauth) in the same instance.

In addition, read the prerequisites as described in the
Omnibus Redis HA document since they provide some
valuable information for the general setup.

Step 1. Configuring the master Redis instance

## Define a `bind` address pointing to a local IP that your other machines
## can reach you. If you really need to bind to an external accessible IP, make
## sure you add extra firewall rules to prevent unauthorized access:
bind10.0.0.1## Define a `port` to force redis to listen on TCP so other machines can
## connect to it (default port is `6379`).
port6379## Set up password authentication (use the same password in all nodes).
## The password should be defined equal for both `requirepass` and `masterauth`
## when setting up Redis to use with Sentinel.
requirepassredis-password-goes-heremasterauthredis-password-goes-here

Restart the Redis service for the changes to take effect.

Step 2. Configuring the slave Redis instances

## Define a `bind` address pointing to a local IP that your other machines
## can reach you. If you really need to bind to an external accessible IP, make
## sure you add extra firewall rules to prevent unauthorized access:
bind10.0.0.2## Define a `port` to force redis to listen on TCP so other machines can
## connect to it (default port is `6379`).
port6379## Set up password authentication (use the same password in all nodes).
## The password should be defined equal for both `requirepass` and `masterauth`
## when setting up Redis to use with Sentinel.
requirepassredis-password-goes-heremasterauthredis-password-goes-here## Define `slaveof` pointing to the Redis master instance with IP and port.
slaveof10.0.0.16379

Restart the Redis service for the changes to take effect.

Go through the steps again for all the other slave nodes.

Step 3. Configuring the Redis Sentinel instances

Sentinel is a special type of Redis server. It inherits most of the basic
configuration options you can define in redis.conf, with specific ones
starting with sentinel prefix.

Assuming that the Redis Sentinel is installed on the same instance as Redis
master with IP 10.0.0.1 (some settings might overlap with the master):

## Define a `bind` address pointing to a local IP that your other machines
## can reach you. If you really need to bind to an external accessible IP, make
## sure you add extra firewall rules to prevent unauthorized access:
bind10.0.0.1## Define a `port` to force Sentinel to listen on TCP so other machines can
## connect to it (default port is `6379`).
port26379## Set up password authentication (use the same password in all nodes).
## The password should be defined equal for both `requirepass` and `masterauth`
## when setting up Redis to use with Sentinel.
requirepassredis-password-goes-heremasterauthredis-password-goes-here## Define with `sentinel auth-pass` the same shared password you have
## defined for both Redis master and slaves instances.
sentinelauth-passgitlab-redisredis-password-goes-here## Define with `sentinel monitor` the IP and port of the Redis
## master node, and the quorum required to start a failover.
sentinelmonitorgitlab-redis10.0.0.163792## Define with `sentinel down-after-milliseconds` the time in `ms`
## that an unresponsive server will be considered down.
sentineldown-after-millisecondsgitlab-redis10000## Define a value for `sentinel failover_timeout` in `ms`. This has multiple
## meanings:
##
## * The time needed to re-start a failover after a previous failover was
## already tried against the same master by a given Sentinel, is two
## times the failover timeout.
##
## * The time needed for a slave replicating to a wrong master according
## to a Sentinel current configuration, to be forced to replicate
## with the right master, is exactly the failover timeout (counting since
## the moment a Sentinel detected the misconfiguration).
##
## * The time needed to cancel a failover that is already in progress but
## did not produced any configuration change (SLAVEOF NO ONE yet not
## acknowledged by the promoted slave).
##
## * The maximum time a failover in progress waits for all the slaves to be
## reconfigured as slaves of the new master. However even after this time
## the slaves will be reconfigured by the Sentinels anyway, but not with
## the exact parallel-syncs progression as specified.
sentinelfailover_timeout30000

Restart the Redis service for the changes to take effect.

Go through the steps again for all the other Sentinel nodes.

Step 4. Configuring the GitLab application

You can enable or disable Sentinel support at any time in new or existing
installations. From the GitLab application perspective, all it requires is
the correct credentials for the Sentinel nodes.

While it doesn't require a list of all Sentinel nodes, in case of a failure,
it needs to access at least one of listed ones.

The following steps should be performed in the GitLab application server
which ideally should not have Redis or Sentinels in the same machine for a HA
setup:

Edit /home/git/gitlab/config/resque.yml following the example in
resque.yml.example, and uncomment the Sentinel lines, pointing to
the correct server credentials:

# resque.yamlproduction:url:redis://:redi-password-goes-here@gitlab-redis/sentinels:-host:10.0.0.1port:26379# point to sentinel, not to redis port-host:10.0.0.2port:26379# point to sentinel, not to redis port-host:10.0.0.3port:26379# point to sentinel, not to redis port

In this example we consider that all servers have an internal network
interface with IPs in the 10.0.0.x range, and that they can connect
to each other using these IPs.

In a real world usage, you would also setup firewall rules to prevent
unauthorized access from other machines, and block traffic from the
outside (Internet).

For this example, Sentinel 1 will be configured in the same machine as the
Redis Master, Sentinel 2 and Sentinel 3 in the same machines as the
Slave 1 and Slave 2 respectively.

Here is a list and description of each machine and the assigned IP:

10.0.0.1: Redis Master + Sentinel 1

10.0.0.2: Redis Slave 1 + Sentinel 2

10.0.0.3: Redis Slave 2 + Sentinel 3

10.0.0.4: GitLab application

Please note that after the initial configuration, if a failover is initiated
by the Sentinel nodes, the Redis nodes will be reconfigured and the Master
will change permanently (including in redis.conf) from one node to the other,
until a new failover is initiated again.

The same thing will happen with sentinel.conf that will be overridden after the
initial execution, after any new sentinel node starts watching the Master,
or a failover promotes a different Master node.

Example configuration of the GitLab application

Edit /home/git/gitlab/config/resque.yml:

production:url:redis://:redi-password-goes-here@gitlab-redis/sentinels:-host:10.0.0.1port:26379# point to sentinel, not to redis port-host:10.0.0.2port:26379# point to sentinel, not to redis port-host:10.0.0.3port:26379# point to sentinel, not to redis port

# resque.yamlproduction:url:redis://:myredispassword@gitlab-redis/sentinels:-host:10.0.0.1port:26379# point to sentinel, not to redis port-host:10.0.0.2port:26379# point to sentinel, not to redis port-host:10.0.0.3port:26379# point to sentinel, not to redis port